This invention relates generally to an aquaculture method and apparatus and, more particularly, to an aquaculture method and apparatus employing a cage formed out of a vertically contractible, non-buoyant mesh material.
Aquaculture is a rapidly expanding industry providing increasing quantities of various fish products. In comparison to conventional commercial fishing techniques, aquaculture offers the advantages of a predictable harvest and reduced labor and equipment cost. However, present systems are plagued with a variety of serious problems.
Typical aquaculture systems utilize weighted, fiber mesh nets suspended in a suitable water body by floatation rings. After a given growth period, the cage is lifted to the surface of the water body for harvest of a retained fish crop. Serious losses are caused in such aquaculture systems by large aquatic predators such as sharks, tuna and seals that easily penetrate the fiber mesh nets and feed upon the resident fish. Further losses occur when remaining fish escape through the openings created in the net by the predators.
To alleviate the predator problem, many aquaculture systems provide an auxiliary net that surrounds and is spaced from the fish retaining primary net. However, such protective netting also is subject to penetration by predators. Other disadvantages of currently employed fiber mesh nets are a requirement for extensive anchoring and a tendency for the flexible nets to be displaced by tidal flows and thereby undesirably crowd resident fish.
The object of this invention, therefore, is to provide an improved aquaculture system that reduces problems inherently present in existing systems.